1. Field of the Invention
The present invention relates to a valve and more particularly to a means and method for assuring tight sealed closure of the valve in the event of fire and failure of the normal sealing means.
2. Description of the Prior Art
Valves employing pivotal closure elements, such as butterfly valves, are widely used throughout industry for fluid handling and control and in particular in ventilation systems. The butterfly valves generally have a resilient sealing means which engages a rigid metal portion of the valve to form a seal when the valve closure member is in the closed position. The seal is at least partially due to the deflection or resiliency of the sealing means, which is carried by either the valve disk or the valve body. A problem would arise if the valve or the fluent material passing therethrough is suddenly elevated to a high temperature, such as in the case of fire, when it is necessary to have such valves shut with assured effective sealing in order to prevent further combustion and/or discharge of the products of combustion.
While there are many known mechanisms and methods for rapidly shutting valves in the event of fire, merely shutting the valve will not necessarily obviate further problems since the elevated temperature of the fire may cause destruction of the sealing member, such as an O-ring, in the valve. Since the conventional valve does not normally form a complete metal-to-metal seal, the destruction of the sealing member would in fact leave sufficient space for the passage of either the fuel to sustain combustion or the products of combustion, either case being equally as undesirable.